If you're a seasoned entrepreneur, you're likely expert at something other entrepreneurs need help with -- be it complex accounting issues, or how to market an app to customers. So, the odds are high that someone out there will not only value your expertise, but be willing to pay for it.

After all, how many times have you been stuck on a complex issue you knew could be solved by someone who's already "been there"? You certainly aren't the first (and you won't be the last).

And, let's face it, there are times in almost every entrepreneur's business journey, particularly at the start, when some extra cash could come in handy. So, how can you parlay your wisdom, knowledge and experience into a paycheck without sidelining your ambition?

Thankfully, there's an app for that.

For years, being a freelance consultant meant building a long list of connections and clients, but the new generation of consulting apps and marketplaces has taken much of the friction out of finding and retaining freelancing clients. Here are three such platforms and an assessment of which ones work best for different goals.

Clarity

Clarity gathers together a community of vetted experts and entrepreneurs with proven track records who are building, or working on, successful startups. They're willing to talk about it -- for a price. Clarity allows you to get a real live human expert on the phone to answer questions about your business, making it best for users with a specific solution they want to achieve.

The best experts on the platform have years of experience in solving issues in a particular facet of business.

One of the things that makes Clarity unique is its emphasis on face-to-face communication via video chat. According to the website, more than 73,000 calls have been conducted via the platform thus far.

If you feel that your skill set and experience would make you a good addition to Clarity's consultant pool, apply using your LinkedIn profile to join. Pricing works by you setting your own rate per minute, and Clarity taking a 15 percent commission on all calls.

Whether or not you ecome a Clarity consultant, the site is well worth a look for any entrepreneur looking to expand his or her knowledge base. There is a vast video archive of experts giving presentations on a wide variety of topics, which may well spark some ideas and insights relevant to your own business.

There are also question and answer forums, similar to those on Quora, except that the answers are given by Clarity-approved experts.

Moonlighting

Moonlighting is a freelance marketplace that gives consultants the tools they need to build a personal brand. This includes everything from a custom business landing page, optimized for mobile, to unlimited proposal templates and invoicing materials.

One of the biggest reasons to like Moonlighting is that it differs from similar platforms, in not charging a commission on your work. Instead, freelancers pay either a monthly or yearly fee that gives them access to a powerful suite of tools for unlimited invoicing, listings and proposals as well as advanced marketing functionality. This fixed rather than variable cost structure means you aren't penalized the more work you do. Plus, there is a limited free option if you want to test out the app before making a financial commitment.

Another Moonlighting tool useful to entrepreneurs is its Moon$hot crowd-funding platform. Unlike Kickstarter and similar sites, Moon$hot allows fund-raising without requiring that the entrepreneur meet specific goals. For example, if your fund-raising goal is $10,000, and you only receive pledges totaling $9,000, you get to keep that $9000 minus the 5 percent commission fee on each donation (plus another payment-processing fee).

While Moon$hot lacks the big visibility of a Kickstarter or IndieGoGo, it has less stringent requirements as to what type of projects can be funded, and there are no requirements to offer rewards. Therefore, if you have a good distribution network, Moon$hot might be a good option for your project.

Whether you're considering converting some of your expertise into consulting revenue or looking for funding for your next project, this marketplace is worth a look.

Upwork

Along with Fiverr, Upwork is perhaps the best known freelance marketplace. It connects millions of freelancers with clients from around the globe. Freelancers and potential clients can list services they offer or services they require. Freelancers pay a commission to Upwork on a multi-tiered sliding scale, according to those freelancers' size. The more work you do for one specific client, the lower the percentage you'll pay.

Virtually every specialty can be found on Upwork, making it far less focused than Clarity. Clarity is geared specifically toward busy entrepreneurs looking to share their wisdom and make some extra income by giving actionable advice on areas where they have useful experience.

Upwork's more traditional work-for-hire structure may lend itself better to freelancers seeking to become full-time members of the gig economy rather than those looking to fund their own business journey. Freelancers on Upwork are hired largely based on ratings from previous employers. Keep in mind that it's a highly competitive marketplace and these ratings will take some time to build up.

Final thoughts

The journey toward success for any entrepreneur is sure to come with forks in the road. There's nothing wrong with that -- in fact, it can be part of the fun.

Here, I've described three different approaches to consulting work and their corresponding apps that can help connect burgeoning consultants with clients willing to pay for your expertise.

Finally, it's common to have a "side hustle" as you build your dream -- I've personally offered my services through such apps. Don't hesitate to consider these as alternative sources of funding while you're working hard to make your entrepreneurial goals a reality.

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Kathleen, Founder and CEO of Grayce & Co, a media and marketing consultancy, can help you develop a brand strategy, build marketing campaigns and learn how to balance work and life.